JPH1048910A - Seamless tube coated electrification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seamless tube coated electrification roller excellent in the surface characteristic in which a stable electric characteristic can be obtained. SOLUTION: In an electrification roller 2 which is abutted on a body 1 to be electrified for electrifying the body 1 by applying a voltage and which is made up of a electrification supporting body 13 and a semiconductive seamless tube 15 coating the outer circumference thereof, the seamless tube 15 is made by extruding a semiconductive thermoplastic resin compound into a tubular shape by means of an extruder, and it is brought into contact with a tube-inside- diameter regulating member that has been arranged inside the tube for regulating temperature, and further it is formed by the method that is received while maintaining the tubular shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seamless tube-coated charging roller for charging a member to be charged such as a photoreceptor or an intermediate transfer member used in an electrophotographic or electrostatic recording process in a copying machine, a printer or the like.

[0002]

2. Description of the Related Art FIG. 1 is a side view of an electrophotographic apparatus. In FIG. 1, reference numeral 1 denotes a photosensitive drum as a member to be charged, and reference numeral 6 denotes a conductive belt as an intermediate transfer member. Around the photosensitive drum 1, a charging roller 2 as a charging device, an exposure optical system 3 using a semiconductor laser or the like as a light source, a developing device 4 containing toner, and a cleaner 5 for removing residual toner are provided. An electrophotographic process unit is arranged.

Next, the operation will be described. First, the surface of the photosensitive drum 1 rotating in the direction of the arrow is uniformly charged by the charging roller 2. Next, an electrostatic latent image corresponding to an image obtained by an image reading device or the like (not shown) is formed on the photosensitive drum 1 by the optical system 3. The electrostatic latent image is developed into a toner image by the developing device 4. The toner image is electrostatically transferred to the conductive belt 6 by the electrostatic transfer device 10 and transferred to the recording paper 11 between the transport roller 9 and the pressing roller 12.

Conventionally, a corona discharge method has been employed as a charger for charging a photosensitive member or a transfer belt. In the corona discharge method, the surface of the photosensitive drum is
This is to impart a photosensitivity by applying a corona discharge from a corona discharger to perform a charging process. This method is generally 5-8K
Since a high voltage of V is applied to the metal wire, the ozone generated by the discharge affects the performance of the photoreceptor and affects the human body. A law is being developed. (Japanese Unexamined Patent Publication No.
As a roller used in such a charging device, a roller in which a conductive support (metal shaft core) and its outer periphery are coated with a conductive elastic layer is used. .

In this case, as the conductive elastic layer, silicone rubber, ethylene propylene rubber, nitrile rubber,
It has been proposed to be formed by a composition in which conductive powder such as carbon is mixed into synthetic rubber such as urethane rubber. However, conductive rubber has a semiconductive It is difficult to control in the area. In addition, there is a problem that the electric resistance value changes depending on the environment and it is difficult to perform charging uniformly. It is also difficult to reduce the surface roughness by polishing. For this reason, there has been a problem that minute irregularities form a space gap between a roller and a member to be charged such as a photoreceptor or an intermediate transfer member, thereby causing poor charging. In view of this, a semiconductive roller has been proposed which is made by covering a contracted or uncontracted seamless tube having excellent surface properties. (JP-A-3-59682, JP-A-5-248426)

[0006]

However, since the seamless tube for covering the roller is generally a shrinkable tube, it shrinks excessively due to heat, so that wrinkles are generated on the roller at the time of shrinkage. It is not only very difficult to make a tube with a controlled resistance value because it is molded, but also a carbon chain is connected during shrinkage, the resistance changes significantly, and the electrical resistance cannot be controlled. Not suitable.

Also, the resistance distribution deteriorates probably because the residual stress generated when the shrinkable tube is formed is not uniform all around the tube. For this reason, there has been a problem that uniform charging is not performed and unevenness occurs in an image due to transfer failure of toner due to uneven charging. Further, an unshrinkable tube has been proposed as a seamless tube for covering the roller. However, the seamless tube for coating the roller is formed by winding a composition in which conductive particles such as carbon are dispersed in synthetic rubber such as epichlorohydrin rubber, nitrile rubber, acrylic rubber, urethane rubber, silicone rubber, and fluorine rubber around a metal roller. A method of forming the molded body by separating the core from the core while turning over the inner surface of the rubber portion, or immersing the substrate in a coating material in which nylon and conductive powder are dissolved and dispersed, and pulling up the substrate. The material is limited because it is a forming method by dipping in which a base material is inserted into a tubular shape by forming a coating material or dissolving a coating material to form a tube.

Furthermore, in the case of a seamless tube made of conductive rubber, since a process such as a crosslinking treatment is performed at the time of molding, the carbon chain moves arbitrarily at the time of crosslinking, and the resistance value is controlled uniformly in a semiconductive region. Is difficult. In addition, there is a problem that the electric resistance value changes depending on the environment and it is difficult to perform charging uniformly. In the case of a seamless tube by dipping using nylon or the like, the coating material in which the conductive particles are dissolved sinks in the solution, the dispersion in the solution is uneven, and it is difficult to control the resistance value to be semiconductive. . Not good for working environment due to use of solvent. There is also a problem that the solvent volatilizes even after molding, and the resistance value changes due to environmental fluctuations.

On the other hand, the formation of a seamless tube by extrusion has been proposed. In general, a thin-walled small-diameter tube having a diameter of 30 mm or less is formed by an outsizing method. Absent. Therefore, when the roller is mounted on the roller, there is a problem that a difference occurs when the inner diameter of the tube is small and a large portion is contracted, and there is a problem that a partial difference occurs in the electric resistance. However, since the material is regulated by the mold on the outside of the tube, if there is a foreign substance or a gel-like material, the outside becomes concave, and there is a problem that dust such as toner easily enters and it is difficult to clean the attached toner and dust. . Due to external regulations, the inner perimeter may vary due to slight pulling fluctuations and extrusion fluctuations, and it may not be possible to insert the roller. In addition, the slight difference in the inner diameter will cause the resistance value for each shrinkage to vary, resulting in uniform performance. There was a problem that it could not be obtained.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photoconductor used in an electrophotographic or electrostatic recording process in a copying machine, a printer, or the like, and a charging roller for charging an object to be charged such as an intermediate transfer member. It is another object of the present invention to provide a seamless tube-covered charging roller having excellent surface characteristics that can provide stable electric characteristics without causing charging unevenness or the like. Therefore, the present inventors have found that a change in the resistance value of the roller occurs when the seamless tube is coated on the roller, and the cause of the change is that the inner diameter accuracy of one seamless tube is non-uniform, so that the change is partially caused. It was found that shrinkage unevenness occurs when mounted on the roller, and as a result, the distance between the carbons due to shrinkage does not decrease uniformly throughout the tube,

In order to produce a roller having a smooth surface and a uniform electric resistance, the outermost seamless tube should be a seamless tube formed by an internal regulation system and having a low shrinkage rate within a certain range of inner diameter accuracy. Was found to be important. Since the outer surface of a seamless tube made by the internal regulation method does not become rough, a roller having a smooth surface and a uniform electric resistance can be obtained by coating the seamless tube made by this method onto a roller.

That is, the gist of the present invention is to provide a charging device comprising a conductive support and a semiconductive seamless tube covering the outer periphery of the conductive support, which is charged by applying a voltage to the member to be charged. In the roller, the seamless tube, the semiconductive thermoplastic resin composition is extruded into a tube by an extruder, and is brought into contact with a temperature-controlled tube inner diameter regulating member arranged inside the tube,
The present invention further provides a seamless tube-coated charging roller, which is a seamless tube formed by a method of drawing while maintaining a tubular shape.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. (1) Configuration of Charging Roller The charging roller of the present invention has a configuration in which a low heat-shrinkable seamless tube whose inner diameter is controlled is mounted on the outer periphery of a conductive support. (2) Conductive Support As the conductive support, a metal material such as aluminum or sus is generally used because the rigidity of the roller is required, but the conductive support is not limited thereto. (3) Conductive Elastic Body In the charging roller of the present invention, the outer periphery of the conductive support may be covered with a conductive elastic body, and the outer periphery may be further covered with a semiconductive seamless tube. The conductive elastic body used in this case is formed of a composition obtained by mixing a conductive powder such as carbon black or metal powder with silicone rubber, ethylene propylene rubber, nitrile rubber, urethane rubber, or the like, but is not limited thereto. It will not be done. Since the charging roller charges the photosensitive member and the intermediate transfer member while contacting them, it is desirable that the hardness of the conductive elastic body be low.

(4) Seamless Tube The seamless tube used in the present invention must be a seamless tube formed by regulating the inside of the tube. If the accuracy of the inner diameter is not within a certain range,
When the roller is attached to the roller due to thermal contraction or the like, the roller is excessively contracted over the entire circumference, so that the resistance value of the roller surface partially varies, and the electric resistance of the roller does not fall within a certain range.

An example of a method for producing a seamless tube whose inside is regulated is, for example, an internal cooling mandrel method of a downward extrusion method in which the inside diameter of an extruded tube is controlled by a high precision without being affected by gravity by a continuous melt extrusion molding method. can give. The extrusion device of the internal cooling mandrel type can have the following configuration, for example. (JP-A-4-2553
The upper part of the support pipe is fixed coaxially to an annular die attached to the extruder, and a mandrel for internal cooling is coaxially fixed to the lower part of the support pipe. Below the mandrel, a plurality of nip rolls for pulling the tube are arranged outside the tube.

The annular die is preferably a spiral die. In a spider die, thickness unevenness is likely to occur at the resin merging portion, and that portion is easily broken. A spider die cannot be used particularly when making a resistance control tube using a carbon dispersed material. This is because the turbulence of the shear rate distribution in the die affects the resistance value of the tube, so that the shear is extremely different at the resin converging portion of the spider mark. The extrusion direction is preferably vertical. In the case of horizontal direction, it hangs down by its own weight and impairs roundness. In order to cool in a tube state and to cool to a predetermined diameter, it is desirable to use an internal cooling mandrel system with an accurate inner diameter. With the external sizing method, the accuracy of the inner diameter is not high. When covering the roller, the inner diameter accuracy of the tube is important. In order to take off the tube without creases, it is necessary to keep a circle with a plurality of nip rolls from the outside while maintaining the circle. Therefore, it is desirable to adopt a system in which a core is inserted into the support tube rod in an annular die, and the seamless tube is pulled out by a nip roll while contacting the outside of the core. If the tube diameter is small, the nip roll cannot be inserted inside. If the tube diameter is small, only the middle part cannot be nipped. Then it bends. A core is required when a thin (thin) seamless tube is to be pulled without folds. The extruded seamless tube must have necessary conductivity, uniform thickness, inner diameter accuracy, and mechanical strength in an unstretched state. This means that although the mechanical strength can be expected to be improved by the stretching operation, the uniformity of conductivity is impaired, the durability is impaired because the film is easily torn in the stretching direction, This is because a problem such as a change in the resistance value during heat shrinkage occurs.

(5) The resin composition applied to the seamless tube in the present invention is a thermoplastic resin, and includes a resin containing a conductive filler. As the thermoplastic resin, ethylene (high density, medium density, low density, linear low density), propylene ethylene block or random copolymer, rubber or latex component such as ethylene / propylene copolymer rubber, styrene / butadiene rubber , Styrene-butadiene-styrene block copolymer or hydrogenated derivative thereof, polybutadiene, polyisobutylene, polyamide, polyamideimide, polyacetal, polyarylate, polycarbonate, polyphenylene ether, modified polyphenylene ether, polyimide, liquid crystalline polyester, polyethylene terephthalate, Polysulfone, polyethersulfone, polyphenylene sulfide, polybisamide triazole,
Polybutylene terephthalate, polyetherimide, polyetheretherketone, acrylic, polyvinylidene fluoride, polyvinyl fluoride, ethylene tetrafluoroethylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene hexafluoropropylene copolymer, tetrafluoroethylene Perfluoroalkyl vinyl ether copolymer, polytetrafluoroethylene, fluoro rubber, alkyl acrylate copolymer, polyester ester copolymer, polyether ester copolymer, polyether amide copolymer, olefin copolymer, polyurethane Copolymers or a mixture thereof are used.

Particularly preferred resins for coating the charging roller are fluorine resins such as polyvinylidene fluoride, polyvinyl fluoride, ethylene tetrafluoroethylene copolymer, chlorotrifluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ether copolymer. And fluorine rubber are also preferred to prevent contamination from toner and the like.Ether thermoplastic resins such as polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyester ester copolymer, and polyether ester copolymer are preferred. This is preferable because the electric resistance value is small and stable in characteristics.

As the conductive filler, at least one selected from carbon black, graphite, carbon fiber, metal powder, conductive metal oxide, organometallic compound, organometallic salt, conductive polymer or the like, or at least one of these, is selected. Those comprising a mixture are preferred. Among them, carbon black is particularly preferred. Examples of the carbon black include carbon black such as acetylene black, furnace black, and channel black. Acetylene black excellent in dispersibility is particularly preferable so as not to impair the appearance of the film.

The amount of carbon black varies depending on the type of carbon black. In the case of acetylene black, the amount is preferably 3 to 25 parts by weight based on 100 parts by weight of the thermoplastic resin. 10
Parts by weight are preferred. Below the above range, poor conductivity,
Above the above range, the appearance of the product is deteriorated, and the material strength is undesirably reduced.

[0021] The resin composition may contain various additional components to be added to the usual resin composition, as long as the object of the present invention is not hindered. Such components include antioxidants, lubricants, release agents, and the like. As long as the effects of the invention are not significantly impaired, the following additional components other than those described above may be further added. Thermoplastic resins, thermosetting resins, and various fillers include, for example, calcium carbonate, talc, mica, silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, zinc oxide, zeolite, wollastonite, diatomaceous earth , Glass beads, bentonite, montmorillonite, asbestos, hollow glass spheres, graphite, molybdenum disulfide, titanium oxide, aluminum fiber, stainless steel fiber, brass fiber, aluminum powder, wood powder, rice hull, graphite, metal powder, conductive metal Fillers such as oxides, organometallic compounds, and organometallic salts can be used. As the additives, for example, antioxidants (phenol-based, sulfur-based, etc.), lubricants, various organic and inorganic pigments, ultraviolet absorbers,
Examples include an antistatic agent, a dispersant, a neutralizing agent, a foaming agent, a plasticizer, a copper damage inhibitor, a cross-linking agent, and a flow improver.

(6) Conductivity of Seamless Tube As the seamless tube for coating the charging roller, the surface resistivity is 1 × 10 ³ to 10 ¹⁵ Ω / □, and the volume resistivity is 1 × 10 ³ to 10 ¹⁵ Ω ·. cm. If the conductivity is too low, the charging member may be broken by applying a voltage, and if the conductivity is too high, the charging property may decrease.

(7) Variation in conductivity of the seamless tube The variation in the conductivity of the seamless tube is such that when the maximum value is not less than 100 times the minimum value, the charging unevenness appears in the image unevenness when used for charging. Can not do.
Preferably it is within 10 times. (8) Inner Diameter Accuracy of Seamless Tube The variation in the inner diameter of the seamless tube is preferably within ± 0.5% of the average inner diameter of the tube. 0.
When it exceeds 5%, when the seamless tube is mounted on the roller by heat shrinkage, air tends to be entrained or wrinkles are generated at a large inner diameter, and uniform charging tends to be hardly performed. Preferred inner diameter accuracy is ±
It is within 0.3%. More preferable inner diameter accuracy is ± 0.
It is within 1%.

(9) Outer Surface Roughness of Seamless Tube The roughness of the seamless tube is preferably within 3 microns as a ten-point average roughness. If the diameter is larger than 3 microns, toner or dust enters the tube surface, and the charged portion is not uniform, so that the tube cannot be used continuously for a long time.
More preferred roughness of the seamless tube is within 1 micron. (10) Heat Shrinkage of Seamless Tube The heat shrinkage of the seamless tube is preferably 10% or less. If it exceeds 10%, the electric resistance tends to fluctuate.
In addition, as long as the heat absorption rate is 10% or less, the presence or absence of stretching of the seamless tube does not matter.

(11) Thickness of the seamless tube The thickness of the seamless tube is not less than 25 μm and not more than 1000 μm.
m or less, more preferably 50 μm or more and 200 μm or less. If the thickness is less than 25 μm, wrinkles when mounting the seamless tube to the roller are not preferable.
On the other hand, if the thickness exceeds 1000 μm, the seamless tube becomes hard, does not deform elastically, becomes less flexible, and damages the photosensitive member, which is not preferable. (12) Method of Attaching to Roller As a method of attaching the seamless tube of the present invention to the roller, a known method such as bonding by an adhesive may be used even if the seamless tube is bonded by heat shrinkage. Since the seamless tube of the present invention has an inner diameter accuracy of ± 0.5% and is not stretched basically, it contracts and adheres to the roller uniformly by heat shrinkage, and there is almost no air entrainment or fluctuation in resistance value. .

[0026]

The present invention will be further described below with reference to specific examples. [Examples 1 to 5] Materials having the composition shown in Table 1 are kneaded with an extruder of 30φ. Kneaded pellets with circular die 4
Using a 0φ extruder, extrude the molten tube below the annular die. The extruded melt tube was mounted on the same axis as the annular die via a support rod. It was brought into contact with the outer surface of a cooling mandrel of φ30 to be cooled and solidified to obtain a seamless tube. Next, the seamless tube was taken out while maintaining the cylindrical shape by the core installed in the seamless tube and the roll installed outside. The obtained tube was heated and shrunk onto a roller having a conductive elastic layer having a surface resistance of 10 ⁷ Ω / □ made of a composition in which carbon was mixed with urethane rubber on the outer periphery of a φ30 metal core to form a charging roller. . When the obtained charging roller was installed in the apparatus shown in FIG. 1 and the image was evaluated, no image unevenness due to charging unevenness occurred.

Comparative Example 1 A charging roller was obtained in the same manner as in Examples 1 to 5, except that the extruded molten tube was cooled and solidified by an outsizing device to obtain a seamless tube. When the obtained charging roller was installed in the apparatus of FIG. 1 and the image was evaluated, image unevenness due to charging unevenness occurred. [Comparative Example 2] A charging roller was obtained in the same manner as in Examples 1 to 5, except that a molten parison was pressed against a mold placed outside using a blow molding apparatus and cooled to obtain a seamless tube. When the obtained charging roller was installed in the apparatus of FIG. 1 and the image was evaluated, image unevenness due to charging unevenness occurred. Comparative Example 3 A charging roller was obtained in the same manner as in Examples 1 to 5, except that the extruded molten tube was obtained as a seamless shrink tube having a shrinkage ratio of 15% by a shrink tube forming method using an outsizing apparatus and a stretching apparatus. Was. When the obtained charging roller was installed in the apparatus of FIG. 1 and the image was evaluated, image unevenness due to charging unevenness occurred.

The materials used in the examples and comparative examples are as follows:
It is as follows. 1. 1. Ethylene tetrafluoroethylene copolymer (trade name “AFLON COP c55AP” manufactured by Asahi Glass Co., Ltd.) 2. PBT (manufactured by Mitsubishi Engineering-Plastics Corporation, trade name “Novadol 5020”) 3. PC (manufactured by Mitsubishi Engineering-Plastics Corporation, trade name “Iupilon E 2000”) Acetylene black (Denka Black, manufactured by Denki Kagaku)

Experiments and evaluation methods in Examples and Comparative Examples are as follows. 1. Surface specific resistance (Ω / □) Using a surface resistance meter Hiresta HA probe (manufactured by Yuka Denshi Co., Ltd.), the measurement was performed at a measuring voltage of 500 V and a measuring time of 10 seconds at a pitch of 10 mm in the circumferential direction of the tube. 2. Inner diameter accuracy Cut out the seamless tube, measure the circumferential dimensions of both ends and the center of the tube with a three-dimensional dimension measuring instrument, and if it is within ± 0.5% of the average inner diameter, ○, ± 0.5% When exceeding, it was evaluated as x. 3. Outer Surface Roughness “Surfcom” manufactured by Tokyo Seimitsu Co., Ltd.
570A ", the ten-point average roughness of the outer surface of the tube was measured. 4. Heat shrinkage After heating at 100 ° C. for 1 hour, the shrinkage when left at room temperature was determined.

[0030]

[Table 1]

[0031]

According to the present invention, in a copying machine, a printer, or the like, a charging roller for charging a photosensitive member used in an electrophotographic or electrostatic recording process, or a charged member such as an intermediate transfer member, causes uneven charging. The present invention can provide a seamless tube-covered charging roller having excellent surface characteristics that does not cause the occurrence of stable electric characteristics.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of an electrophotographic copying machine incorporating a charging roller of the present invention.

FIG. 2 is a schematic sectional view of a charging roller of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (charged body) 2 Charging roller (charging device) 3 Exposure optical system 4 Developing device 5 Cleaner 6 Conductive belt (intermediate transfer body) 7 Transport roller 8 Transport roller 9 Transport roller 10 Electrostatic transfer device 11 Recording Paper 12 pressing roller 13 conductive support 14 conductive elastic body 15 semiconductive seamless tube

Claims (8)

[Claims] 1. A charging roller comprising a conductive support and a semiconductive seamless tube covering the outer periphery of the conductive support, wherein the charging roller is charged by applying a voltage to the member to be charged. A tube is formed by extruding a semiconductive thermoplastic resin composition into a tube by an extruder, contacting the inside of the tube with a temperature-controlled tube inner diameter regulating member, and further pulling the tube while maintaining the tube shape. A seamless tube-coated charging roller, characterized by being a seamless tube. 2. A chargeable roller comprising a conductive support and a semiconductive seamless tube covering the outer periphery thereof, wherein the chargeable roller is brought into contact with the member to be charged and is charged by applying a voltage. The tube has a surface resistance of 10 ³ Ω / □ to 10 ¹⁵ Ω / □ and its maximum value is the minimum value of 10 ³ Ω / □.
A seamless tube-coated charging roller, wherein the charging roller is within 0 times. 3. A conductive support, a conductive elastic body covering the outer periphery thereof, and a semi-conductive body further covering the outer periphery thereof, wherein the conductive support is charged by applying a voltage to the member to be charged. In a charging roller composed of a seamless tube, the seamless tube has a surface resistance of 10 ³ to 10
A seamless tube-coated charging roller, wherein the maximum value is ¹⁵ Ω / □ and the maximum value is within 100 times the minimum value. 4. The charging roller according to claim 1, wherein the inner diameter of the seamless tube is within ± 0.5% of the average inner diameter over the entire width of the tube. 5. The seamless-coated charging roller according to claim 1, wherein the outer surface of the seamless tube has a ten-point average roughness of 3 μm or less. 6. The heat shrinkage of the seamless tube is 10%.
The seamless tube-coated charging roller according to claim 1, wherein: 7. The charging roller according to claim 1, wherein the thickness of the seamless tube is from 25 μm to 1000 μm. 8. The seamless tube-covered charging roller according to claim 1, wherein the seamless tube is attached by heat shrinkage or adhered via an adhesive.